(n.) A lover of mistress.

ace admirer angel babe baby baby-doll beau beaut beloved betrothed boyfriend buttercup captive catch cherub chick chickabiddy conquest coquette corker court crackerjack daisy dandy darb darling date dear deary dilly doll dream dreamboat duck duckling fiancee flame flirt friend heartthrob hon honey honey bunch honey child humdinger inamorata inamorato intended killer-diller knockout ladylove lamb lambkin lollapaloosa love lover lulu make up to paramour peach pet petkins pip pippin precious precious heart pursue snookums spark steady sue sugar sweet sweet patootie sweetie sweetkins sweets the nuts truelove turtledove vamp vampire whiz woo